Soften gelatin in ¼ cup cold water.Mix in a saucepan ½ c. sugar, salt, and milk.Cook over low heat stirring constantly until hot.Remove from heat, stir a little of the hot mixture into the egg yolks.Then combine yolks with rest of the mixture.Return to low heat and bring to a boil, stirring.When it comes to a boil, remove from heat immediately.Add gelatin and let cool ‘til set.Once set, beat with rotary beater until smooth.Blend in rum and set aside.Whip cream until thick and fold into gelatin mixture.Beat egg whites, cream of tartar until stiff.Add sugar and blend into gelatin mixture with a spoon or spatula.Pour into pie shell and refrigerate.